The present invention relates to an endoscope system, and an illuminating device to be employed in the endoscope system.
It has been known that human tissues fluoresce when illuminated with excitation light. The wavelength range of the excitation light is a range of 380-480 nm, and the wavelength range of the fluorescent light emitted by the tissues is a range of 480-600 nm. The fluorescent light emitted by diseased tissues such as cancerous ones has less intensity than that emitted by normal tissues if they are illuminated with the predetermined excitation light. Therefore, conventionally, a fluorescent endoscope system utilizing-the above characteristics has been developed and used. Such an endoscope system has, as shown in FIG. 4, a fiber scope system 1, an illuminating device 8 connected to the fiber scope 1, and an image capturing device 3.
The fiber scope 1 includes an insertion portion 11 to be inserted in a human cavity, an operation unit 12 connected to the insertion portion 11. and a connecting tube 13 connected to the operation unit 12. At the distal end side surface of the insertion portion 11. three through openings are formed, one of which is used as a forceps outlet 14a, and an illumination lens 15a and an objective lens 16a are fitted in the other openings, respectively.
An end of the operation unit 12 is connected to the proximal end of the insertion portion 11. An eyepiece optical system 16c is accommodated in the operation unit 12. Inside the insertion portion 11 and the operation unit 12, an image guide fiber bundle 16b (hereinafter referred to as an image guide) is inserted. The image guide 16b is arranged such that the tip end surface thereof faces the objective lens 16a, and the proximal end surface faces the eyepiece optical system 16c. 
An end of the connection tube 13 is connected to a side surface of the operation unit 12, and the other end of the connection tube 13 is connected to the illuminating device 8. Inside the insertion portion 11, the operation unit 12, and the connection tube 13, a light guide fiber bundle 15b (hereinafter referred to as a light guide) is inserted.
The Illuminating device 8 is provided with a xenon lamp 81, a reflector 82, an infrared cut off filter 83 and a light source side band pass filter 84. The xenon lamp 81 emits white light having a relatively large intensity. The reflector 82 is arranged such that the white light emitted by the xenon lamp 81 is reflected toward a light receiving surface of the light guide 15b as converging light. Between the xenon lamp 81 and the light receiving surface of the light guide 15b, the infrared cut out filter 83, which prevents radiation of heat by removing Infrared component within the white light, and the light source side band pass filter 84, which allows light having a predetermined wavelength range (e.g., 400 nm-450 nm) that corresponds to the wavelength range of an excitation light, are arranged.
Thus, the light emitted by the xenon lamp 81 and reflected by the reflector 82 enters the light guide 15b with the infrared components being removed by the infrared cut filter 83, and the components other than the excitation light being removed by the band pass filter 84.
The light conducted by the light guide 15b is emerged from a light emerging surface thereof. The light emerged form the light guide 15b is incident on the illumination lens 15a and emerged therefrom as a diverging excitation light. The excitation light Illuminates a wall of a human body cavity, thereby the illuminated portion of the body cavity fluoresces to emit fluorescent light. The fluorescent light emitted by the body cavity as well as the excitation light reflected by the body cavity is incident on the objective lens 16a. The objective lens 16a converges the incident light on the light receiving surface (i.e., the tip end surface) of the image guide 16b to form an image of the illuminated portion, which is transmitted to the eyepiece optical system through the image guide 16b. 
In the image capturing device 3, an optical path along which the light emerged from the eyepiece optical system 16c is defined. The image capturing device 3 includes, along the optical path, a band pass filter 31, a condenser lens 32, an image intensifier 33, an imaging optical system 34 and a camera head 35.
The band pass filter 31 cuts off the reflected excitation light component so that only the fluorescent light component passes therethrough. The condenser lens 32 collects the light passed through the band pass filter 31 and converges the same to impinge on the image intensifier 33. The image intensifier 33 intensifies the incident light. The imaging optical system 34 converges the intensified light to form an image on an image receiving surface of the camera head 35. The camera head 35 converts the optical image formed on the image receiving surface into an electrical image (i.e., an electrical signal), and transmits the electrical signal to a camera control unit 4 (hereinafter referred to as CCU). The CCU 4 converts the electrical signal received from the camera head 35 into an image signal, and displays the image carried by the electrical signal on a monitor 5.
Further to the above, the conventional fluorescent endoscope system is provided with a polychromator 6, and a personal computer 7 connected to the polychromator 6. The polychromator 6 includes a light guide probe 6a. The polychromator 6 detects intensity of light incident on the tip end of the light guide probe 6a on wavelength basis.
The light guide probe 6a is inserted from a forceps inlet opened on the operation unit 12 and inserted through the fiber scope 1, the tip end of the light guide probe 6a being protruded out of the forceps outlet 14a of the insertion portion 11.
The polychromator 6 detects the intensity of the fluorescent light conducted by the light guide probe 6a on wavelength basis, converts the same into electrical signals, and outputs to the personal computer 7. The personal computer 7 displays a graph showing an intensity distribution of the fluorescent light on wavelength basis.
According to the conventional fluorescent endoscope system, the illuminating device 8 is constituted such that the white light is incident on the band pass filter 84 to obtain the excitation light. However, it is impossible to completely remove the components other than the excitation light component from the white light with the band pass filter 84. Therefore, in the conventional fluorescent endoscope system, the light components other than the excitation light component affect the image to be observed.
Alternative to the above-described illuminating device 8, an illuminating device employing a laser light source can be employed. Since the laser is superior in terms of monochromatism, the band pass filter 84 and the like are unnecessary. However, in order to obtain a sufficient intensity as the excitation light, the light source needs to be a large device such as a gas laser device. Further, such a laser device requires a relatively long idling period before it starts emitting light, the light source should be ready in advance, which is troublesome. Furthermore, when the gas laser device is used, an initial cost as well as a maintenance cost becomes relatively expensive.
It is therefore an object of the invention to provide an improved endoscope system employing an illuminating device which is superior in monochromatism, and can be used simply and quickly.
For the above object, according to the invention, there is provided an illuminating device for an endoscope system. The illuminating device emits light toward a light receiving surface of an optical fiber bundle. The light incident on the light receiving surface of the optical fiber bundle is emitted from a light emitting surface thereof for illuminating an object. The illuminating device is provided with a plurality of light emitting elements, each of which emits a directive monochromatic light beam. The light beams emitted by the plurality of light emitting elements are incident on the light receiving surface of the optical fiber bundle within an angular aperture thereof.
Since a plurality of light emitting elements which emit directive and monochromatic light beams, even if a light beam emitted by each light emitting element has relatively low intensity, the resultant light collected on the light receiving surface of the optical fiber bundle has sufficient intensity. Thus, monochromatic light beam having a sufficient intensity can be obtained with a relatively compact structure.
According to another aspect of the invention, there is provided an endoscope system, which is provided with an illuminating device, an endoscope, an optical fiber bundle having a light receiving surface and light emitting surface, the optical fiber bundle being inserted through the endoscope, and an illuminating optical system provided at a distal end portion of the endoscope. The light receiving surface of the optical fiber bundle faces the illuminating device, and the light emitting surface of the optical fiber bundle faces the illuminating optical system. The illuminating device is provided with a plurality of light emitting elements, each of which emits a directive monochromatic light beam. The light beams emitted by the plurality of light emitting elements are incident on the light receiving. surface of the optical fiber bundle within an angular aperture thereof. The light emitted from the light emitting surface of the optical fiber bundle is directed toward an object through the illuminating optical system.
Optionally, in either of the above illuminating device or the endoscope system, the plurality of light emitting elements may be arranged on a substantially spherical concave plane, whose center is located substantially on the central axis of the light receiving surface of the optical fiber bundle.
In this case, it is beneficial to provide a mount member on which the plurality of light emitting elements are fixed. The mount member may be provided with a surface formed to have the substantially spherical concave plane as defined above. The surface may face the light receiving surface of the optical fiber bundle, and the plurality of light emitting elements are mounted on the surface of the mount member.
With this structure, the optical path for each light emitting element can be adjusted easily.
In particular case, the plurality of light emitting elements are light emitting diodes. Alternatively, the plurality of light emitting elements are a plurality of laser diodes.
In particular, each of the plurality of light emitting elements emits a light beam whose wavelength is within a range of 380-480 nm, preferably, 400-450 nm. In this case, the emitted light is used as excitation light. The human tissues fluoresce upon incidence of the excitation light.